Exposure to ultraviolet (UV) radiation is known to provide a variety of undesirable effects such as photoaging and photodamage of the skin, and in more extreme cases, cutaneous squamous cell or basal cell carcinoma and malignant melanoma. UV radiation generally encompasses light in the wavelength range of 200-400 nm., with UVA having a wavelength of about 320-440 nm., UVB a wavelength of 290-320 nm., and UVC a wavelength of less than about 280 nm. Acute UV exposure causes solar erythema or sunburn, and is associated with formation of dyskeratotic cells (also called sunburn cells) in the epidermis. Sunburn cells are epidermal cells with an eosinophilic cytoplasm and either no nucleus or a contracted, irregular, nucleus, when stained with hematoxylin and eosin. The formation of sunburn cells is believed to indicate damage to cellular DNA by UV radiation, and in particular UVB radiation.
Traditional sunscreen compositions containing titanium dioxide and chemical sunscreens do provide some degree of protection against formation of sunburn cells. However, these products still permit formation of significant numbers of sunburn cells in skin which is exposed to UV radiation. U.S. Pat. No. 5,140,043 teaches that ascorbic acid containing compositions are capable of reducing sunburn cell formation in the skin of Yorkshire swine, however there is no indication of the effects of such compositions on human skin.
Most unexpectedly, it has been found that ascorbic acid containing compositions are capable of significantly reducing the formation of sunburn cells in mammalian skin when compared to placebo and untreated skin.